Variable pressure gaseous fuel regulator

A system for a gaseous-fueled engine, comprising:

• a gaseous fuel tank;
• a first pressure regulator comprising a high pressure chamber coupled to the gaseous fuel tank, a low pressure chamber coupled to an engine fuel rail, and a reference chamber;
• a second pressure regulator coupled to the reference chamber;
• a first valve controlling fuel flow from the gaseous fuel tank to the engine fuel rail;
• a second valve controlling gaseous fuel flow from the second pressure regulator to the reference chamber;
• a first fuel line coupling the gaseous fuel tank to the high pressure chamber, and a second fuel line coupling the gaseous fuel tank to the reference chamber via the second pressure regulator and second valve;
• a pressure relief conduit coupled to the second fuel line downstream of the second pressure regulator and second valve, and upstream of the reference chamber;
• and
• a controller including memory with instructions therein for adjusting the first and second valves based on a desired fuel rail pressure,
• where the first pressure regulator is a higher pressure regulator and the second pressure regulator is a lower pressure regulator, and
• where the controller further includes memory with instructions therein for, when the first and second valves are actuated, de-actuating the second valve in response to a decrease in desired fuel rail pressure while maintaining the flow of gaseous fuel from the gaseous fuel tank to the fuel rail.